Arrangement in an internal combustion engine

Abstract

A two-stroke internal combustion engine for a motor saw includes a crankcase (12), a fan housing (19) having an impeller (20), and a carburetor chamber (17) having a carburetor (16). An intake passage (15) connects the carburetor to the crankcase and the carburetor chamber is connected via an inlet passage (21) to the fan housing at the outlet side of the impeller for centrifugal purification of combustion air. The carburetor chamber (17) has an opening (22) connected to atmosphere or to a lowpressure zone of the fan housing (19).

I claim: 
     
       1. Arrangement in a two-stroke internal combustion engine, said engine comprising a crankcase (12), a fan housing (19) having an impeller (20), and a carburetor chamber (17) having a carburetor (16), said carburetor being connected to said crankcase via an intake passage (15) and said carburetor chamber being connected via an inlet passage (21) to said fan housing on an outlet side of said impeller, wherein the carburetor chamber (17) has an opening (22) connected to a low pressure zone of the housing (19). 
     
     
       2. Arrangement according to claim 1, wherein the opening (22) is connected via a passage (23) to the fan housing (19) on the inlet side of the impeller (20). 
     
     
       3. Arrangement according to one of claims 1 or 2, wherein the opening (22) has an area of at least about 1.5 cm 2 . 
     
     
       4. Arrangement in a two-stroke internal combustion engine, said engine comprising a crankcase, a fan housing having an impeller, and a carburetor chamber having a carburetor, said carburetor being connected to said crankcase via an intake passage and said carburetor chamber being connected via an inlet passage to said fan housing on an outlet side of said impeller, wherein the carburetor chamber has an opening connected to atmosphere. 
     
     
       5. Arrangement according to claim 4, wherein the carburetor chamber (17) is exposed to an overpressure by combustion air supplied via the inlet passage (21) and that the opening (22) is connected to the atmosphere. 
     
     
       6. Arrangement according to one of claims 4 or 5, wherein the opening (22) has an area of at least about 1.5 cm 2 .